GB631816A - Improvements in servo-motor devices applicable particularly to centrifugal speed governors - Google Patents

Abstract

631,816. Fluid pressure servomotors. AKTIEBOLAGET ATLAS DIESEL. Jan. 20, 1947, No. 1805. Convention date, Oct. 29, 1946. [Class 135] [Also in Groups XXVI and XXXIV] A fluid-pressure servomotor comprising a singleacting piston &c. interposed in a spring system, the outer ends of which are in contact with fixed abutments is controlled by a valve including two relatively movable members for controlling the flow of working fluid to and from the piston cylinder, one of said members being actuated by a governor, e.g. a speedgovernor, whilst the other is connected to the spring system between a fixed abutment and the piston. The embodiment shown is applied to an internalcombustion engine for controlling the fuel supply thereto in accordance with its speed and comprises a casing 3, housing an engine-driven cup member 22 formed with a recess carrying a single governor weight 25 loosely mounted between the cup and the lower end of a rod 29 which supports a valve plunger 8 arranged for rotation with the cup and capable of axial movement. The plunger 8 co-operates with a ported sleeve 6 formed with a flange 18 which provides an abutment interposed between springs 20, 21 whose other ends abut the lower end of the servo-cylinder 2 and its spring- loaded piston 13 respectively. Ports 7 in the sleeve 6 communicate with a duct 4 supplied with pressure oil, whilst ports 12 coacting with a land 11 of the plunger control the flow of oil to the underside of the piston and the discharge therefrom through the hollow piston rod 15 which is operatively connected to the fuel valve. The working range of the governor is adjustable by a spring 9 disposed between a fixed collar 33 and an adjustable collar 31 movable by a forked lever 36 secured to a manually-actuated shaft 35. To increase the operational speed of the engine, the shaft 35 is rotated anti-clockwise to increase the loading on the spring 9, and clockwise to decrease the engine speed. In operation, on a fall in the set engine speed, the plunger 8 will move downwardly to uncover the upper edges of the ports 12 to drain the cylinder 2 and hence permit the downward movement of the spring-loaded piston 13 and an increased opening of the fuel valve. Conversely, a rise in the set engine speed uncovers the lower edges of the ports 12 to permit the supply of oil to the cylinder 2 to raise the piston 13 and hence decrease the opening of the fuel valve. The springs 20, 21 operate to move the sleeve 6 to follow up the movements of the plunger 8. The servomotor may be used for controlling the main valves for gas, steam or hydraulic motors and for operating braking devices and is suitable for use with either liquid or gaseous fluids.